» Legal Ohm Sample (0060)
Immagini
DESCRIPTION
Exhibit 60 is a legal standard Ohm. It consists of two brass cylinders of different diameters (65 mm and 35 mm) connected together. The external connection is made by two small copper cylinders bent into a U shape and separated by a hard rubber clasp. The value of one ohm was guaranteed for a definite temperature (16.8 °C as indicated on the label) to be confirmed on a thermometer inserted in the hole on top.The international Ohm was defined in 1883 as the resistance offered to a constant electrical current by a column of mercury of length 106,30 cm and of mass 14,4521 grams at 0°C. This unit was abandoned in 1939 in favor of the absolute Ohm: the resistance of a resistor which passes a current of one Ampere when the applied voltage is one volt.
ISCRIZIONI
- Sulla parte superiore: "1 OHM¶
RIGHT AT 16.8 C¶
N°29¶
ELLIOTT BROS¶
LONDON"
BIBLIOGRAPHY
- [1] Balfour Stewart, Haldane Gee,"Lessons in Elementary Practical Physics", Vol.II. Electricity and Magnetism; Macmillan and CO. London, 1887. Pagina 161.
Dati Catalografici
| Data di costruzione: | --- |
|---|---|
| Data di carico: | 1879-08-30 |
| Nr. Inventario: | 1736 (Generale dal 1874) |
| Costruttore: | Elliot Bros |
| Materiale: | rame, ottone, ebanite |
| Dimensioni: | 21 cm x 7 cm x 20 cm |
| Conservazione: | ottimo |